The heat shock genes of Drosphila melanogaster constitute a technically well-suited model system for defining general principles of gene regulation in animal cells. The heat shock genes occupy several chromosomal loci that are coodinately activated by heat and a variety of other treatments. The objectives of this proposal are to identify DNA sequences and proteins involved in regulatory interactions at these loci, and to study the correspondence of these interactions to accompanying alterations in chromosome structure. To accomplish these objectives, four interrelated analyses are to be executed, all using cloned DNA segments: (1) sequencing DNA at sites of transcription initiation of a select set of loci to identify conserved elements, (2) testing the affect of in vitro-induced mutations of such conserved sequences on transcription initiation, (3) mapping specific protein-DNA interactions utilizing a newly devised chemical-crosslinking, gene-purification approach, (4) mapping alterations in chromatin structure which accompany gene activation by partial DNAseI digestion, followed by hybridization with specific cloned DNAs.